Conventional pin- or disk-tumbler locks can be picked by a well-known method with pick tools and tension wrenches. In this lock picking procedure, a tension wrench is used to apply a tension force on the rotational plug of the lock to be picked. The tension force provides the plug (rotational portion or core of the lock) a tendency to rotate toward a lock open direction of rotation. Simultaneously, a pick tool is used to move the tumblers one at a time to the shear line of the lock. When all tumblers are aligned at the shear line, the tension force applied by the wrench causes the plug to rotate toward the lock open position so as to unlock the lock.
As the conventional pin- or disk-tumbler locks have been in use over the past hundred years, their structures and picking methods are well known. Varieties of pick tools and pick guns are commercially available. Continuing use of these locks is at great risk to non-authority picking.
Many so-called high security locks have been invented to guard against lock picking. The drawbacks of these locks are having very complicated structures and requiring very sophisticate precision machining. Consequently, high security locks are expensive and therefore have very limited circulation.